Traditionally, a window covering system includes a headrail, a covering material, a bottom rail and a driving device. The covering material is positioned between the headrail and the bottom rail. The driving device is positioned within the headrail and connected to the bottom rail for driving the bottom rail closer to or further from the headrail in order to expand or collect the covering material.
A downward force due to the weight of the bottom rail and the covering material urges rotational speed of the driving device to increase while the covering material is expanding, whereby causing wearing of mechanical parts in the window covering system or causing the bottom rail to directly hit the object or user located under the bottom rail.